The results of this study provide valuable and previously unavailable information about the prevalence and risk factors of suicidal behaviors around the world. Our results show that although there is substantial variability in the prevalence of suicidal behaviors cross-nationally, there are important cross-national consistencies in the prevalence and risk factors for suicidal behaviors. Most notably, across all countries examined, 60% of the transitions from suicidal ideation to first suicide attempt occurred within the first year of ideation onset. Moreover, consistent cross-national risk factors included: female sex, younger age, fewer years of education, unmarried status, and the presence of a mental disorder, with psychiatric comorbidity significantly increasing risk. Interestingly, the strongest diagnostic risk factors were mood disorders in developed countries, but impulse-control disorders in developing countries.
Several important limitations should be borne in mind when interpreting these results. First, although the overall response rate was at an acceptable level, response rates varied across countries and in some cases were below commonly accepted standards. We controlled for differential response using post-stratification adjustments, but it is possible that response rates were related to the presence of suicidal behaviors or mental disorders, which could have biased cross-national comparisons. Also, although surveys in most countries included nationally representative samples, several surveys (e.g., China, Japan) focused on specific urban areas and so findings from those surveys may not generalize to all regions of those countries. A related limitation is that although we examined suicidal behaviors across 17 countries, several countries/regions with high rates of suicide were not included such as India and South East Asia.24
The inclusion of data from additional countries/regions in future work will significantly enhance our understanding of the factors influencing suicidal behaviors more broadly.
Second, data were based on retrospective self-report of the occurrence and timing of suicidal behaviors, and thus may be subject to under-reporting and biased recall. We also did not collect information from third-party informants to validate respondent reports. On balance, several systematic reviews have demonstrated that adults can recall past experiences with sufficient accuracy to provide valuable information,25,26
and such data are especially useful when prospective data are not available,27
as in the current case. Another limitation is that there may be cultural differences in the willingness to report on suicidal behaviors and in the interpretation of questions about DSM-IV mental disorders. Our results must be viewed with these limitations in mind.
Third, several mental disorders were not adequately assessed in the WMH surveys for various reasons. A few DSM-IV disorders were not assessed in some surveys because they were believed to have low relevance or they were excluded from analyses due to an insufficient number of cases, such as impulse-control disorders in Nigeria; and in some cases disorders were not adequately assessed due to skip logic errors, such as bipolar disorder and substance use disorders in the ESEMeD Surveys.10
Schizophrenia and other nonaffective psychoses were not included in any WMH survey because previous validation studies showed they are overestimated in lay-administered interviews like the CIDI.28
These exclusions are unfortunate because prior research clearly indicates that bipolar and substance use disorders are strongly associated with suicidal behaviors3,6
and suggests that schizophrenia and suicidal behaviors share unique prevalence patterns and are strongly related in developing countries,29
thus the current study might have provided important information in this regard. The measurement of these disorders and the explanation of their relation to suicidal behaviors in both developed and developing countries is one of the most important tasks for future work on this topic.
Fourth, this initial study included only a limited range of risk factors for suicidal behavior. Factors such as individual axis I and axis II disorders and traumatic life events were not examined in this study. Also excluded were potential protective factors such as treatment utilization and social support. The investigation of these and other factors remain important directions for future research.
These limitations notwithstanding, several important findings from this study warrant more detailed comment. Perhaps the most important finding of this study is that there is strong cross-national consistency for several key risk factors for suicidal behaviors. Female gender, young age, and low educational attainment have been identified as risk factors for suicidal behaviors in prior studies,3,6
and the current findings suggest these risk factors may be universal. Future research is needed to determine whether risk of suicidal behaviors is occurring at higher rates among young people, or whether people simply become less likely to report on earlier suicidal behavior with age, due to forgetting or re-interpretation of these earlier events.
Risk of suicide plans and attempts also was highest when suicidal ideation had an earlier AOO and within the first year of ideation. Remarkably, 60% of the transitions from ideation to attempt—as well as from ideation to plan and plan to attempt—occur within the first year of onset of ideation and this result is consistent across all 17 countries. Few studies have examined the probability and speed of transition from ideation to plans and attempts, and this information can be especially useful to health care providers. Another important finding is that the strong relation observed between mental disorders and suicide plans and attempts diminishes when controlling for ideation. Thus, although mental disorders are strong risk factors of suicidal behaviors, factors beyond the mere presence of mental disorders explain the transition from ideation to plans and attempts.
Several recent studies have suggested that mental disorders are less important in the occurrence of suicidal behaviors in developing countries relative to developed countries. Whereas studies in developed countries suggest >90% of those who die by suicide have a diagnosable mental disorder and >60% have a mood disorder in particular,30
rates in developing countries have been suggested to be as low as 60% and 35%, respectively.7
Our results indicate that when the same assessment methods are used cross-nationally, mental disorders are as predictive of suicidal behaviors in developing countries as they are in developed countries, and that comorbidity is an important predictor across all countries. Notably though, impulse-control disorders were stronger predictors than mood disorders in most developing countries. The fact that mood and impulse control disorders have the strongest associations with suicidal behaviors is consistent with prior work highlighting the importance of depressed mood and impulsiveness in the suicidal process,31
and extends these findings cross-nationally. The reason for the difference in the importance of impulse-control disorders between developed and developing countries is unclear and awaits further examination.
Future research must examine factors that might explain the variability in prevalence and also must develop more complex risk and protective models that take into account both common and specific factors for each country/region. From a practical perspective, the similarities observed between developing and developed countries suggest equivalent resources should be devoted to studying and preventing suicidal behaviors in these countries. Currently, however, resources devoted to the treatment of mental disorders in general, and to suicide prevention in particular,9
are lacking in many developing (and developed) countries.7,10
It is important to note, however, that more treatment alone is not the answer. Several recent studies have highlighted that despite significant increases in service utilization among suicidal individuals, the rates of suicidal ideation, plans, and attempts have remained virtually unchanged.4
Moreover, although several different forms of treatment have proven effective at decreasing the likelihood of making suicide attempts, psychosocial treatments have proven less effective at decreasing the likelihood of suicide death.32
Improvements in our ability to predict and prevent suicidal behaviors and suicide deaths are clearly needed and require that we continue to identify the risk and protective factors that influence such behaviors and also that we develop more sophisticated methods for synthesizing and using the information obtained about such factors.